Movable closure for a slot



Aug; 4, 1959 L. DRAGONUK MOVABLE CLOSURE FOR A SLOT 3 Sheets-Sheet 1 Filed May 28, 1956 ///////4//// /l/l/l I INVENTOR.

LEO DRAGONUK 1959- L. DRAGONUK 2,897,888

MOVABLE CLOSURE FOR A SLOT Filed May 2 8, 1956 3 Sheets-Sheet 2 2 l III" 22 2 2 ao n n 20 INVENTOR. LEO DRAGONUK TTORNEIYS Aug. 4, 1959 L. DRAGONUK MQVABLE CLOSURE FOR A SLOT 3 Sheets-Sheet 5 Filed May 28, 1956 m m W.

LEO DRAGONUK United States Patent O 2,s97,s'ss i MOVABLE CLOSURE FOR A SLOT LeoDragonuk, Plymouth Meeting, Pa., assignor to the United States 'of America as represented 'by the Secretary of the Navy Application May 23,1956, Serial No. ss7,93 `5 Claims. (c. 160-99) (Granted under Title 35, U.`s. Code 1952 sec. 266

The `invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The invention relates to a movable closure for a slot, and more particularly to a movable closure for a slot longitudin'ally movable along an elongated opening and arranged to accommodate an element projecting through and movable along 'said opening.

Various devices have been employed in the past to seal or close oli a slot through which a movable element protrudes. Typical means for accomplishing this purpose have included flexible metal strips which are slidable in opposed channels with the aid of power springs or a sectional metal curtain that is fixedly contained in canvas, the ends of which are attached to spring actuated rollers. A more recent development in the art is illustrated in co-pending patent application Serial No. 238,758, of Reid, on which Patent No. 2,811,201 issued October 29, 1957, in which use s made of opposed constant force springs more generally known as Neg'ator springs which are mounted adjacent to the protrudng element with the outer extremites of the springs held fixed .relative to the ends of a slot so that as the protruding element is traversed, the extended lengths of the uncoiled portions of the Neg`ator spring become the slot closures. Each of these devices, however, possesses inherent disadvantages: A device incorporating flexible metal strips is seriously handicapped by the fact that the sliding movement in opposed channels of such a closure produces considerable frictional drag and the metal` strips become easily immobile upon entrance of foreign matter, such as dirt or ice, into the channels. Furthernore, the force exerted by the power spring to which the metal strip must be attached varies with the position of the metal strip, and hence, the protruding element, except for a single position of its slot traversal, is always in an unbalanced state. A device incorporating a sectional metal curtain fixedly contained in canvas is not entirely satisfactory because the size of the slot which can be accommodated in this manner is restricted -by the total length of metal curtain that can be employed,

making arrangements of this type bulky and cumbersome, in addition to the fact that the fabric requires special treatment for protection against extreme service conditions. Slot closures employng "Neg'ator springs which overcome the above-noted problems are somewhat unsatisfactory under particular service conditions where wind buffeting'is encountered or where pressure differentials exist between the inside and the outside of the closure. Under these circumstances the extended lengths of the uncoled portionstof the "Neg'ator" springs that form the slot closure become functionally Unstable, experiencin g undesired displacements and distortons with the conseq ent loss of seal and possible collapse of the slot closure, especially where the structure encompassing the'slotand supporting the slot, closure is a convex surface.

Z,897,888 Patented Aug; 4, 1959 The instant invention is particularly applicable to the type of movable slot closure which utilizes a pair of constant force springs more commonly known by the trade name of Neg'ator. Unique properties possessed by these springsare generally well known but are herein briefly summarized to better understand and appreciate their application as slot closures. A Negator or negative spring is characterized by a spring constant K, which has a zero or negative gradient, in contrast to compression and tension springs, which have positive spring constants, The force deflection characteristics, therefore, may be made constant or receding by a process of Stressing each incremental segment along the length of a strip of spring material from which the spring is manufacured. Other more important properties which characterize the Negator are its high initial force at the instant of deflection and the ability to store and deliver approximately twice as much energy as ordinary spiral or power springs occupying the same space. Functionally, the Negator" is distinguished from previously known springs in that the force generated thereby depends upon the elastic characteristics of each increment of its length, used sequentially from one end to the other, rather than upon the instantaneous elastic characteristics of the entire length. This pecularity of the "Negator becomes readily apparent When Compared with the normal spiral and the normal power spring. In its unrestrained position, the stock of the "Negator" forms a tightly wound solid coil due to the fact that in the stressing process the radius of curvat'ure imparted to each incremental length is less than that of the coiled portions, while the stock of a spiral spring lies intthe coiled position with ample free space between successive layers, and the stock of the power spring lies out flat or nearly so. If the outer end of either the spiral or power spring is held fixed and a torque applied on the shaft holding the inner end, the spring will wind on the shaft. This is not characteristic of the "Negator. If its outer end is held, it can be wound no further. These attributes as herein described find appropriate application in slot closure devices, of which the subject invention is an improved type employing a pair of Neg'ator springs.

The slot closure of the instant invention provides an improved means of aifording an eective seal under very adverse service conditions such as would be encountered, for example, in a turret installation of an aircraft in flight. Deficiencies as enumerated in contemporary slot closures are substantially overcome by the use of Neg'ator" springs that are initially transversely prestressed in manufacture and whose faying edges contain a series of preferably equally spaced perforations that cooperate with a series of corresponding pins which project from the supporting structure along both sides of the slot and engage the perforations in the springs as the springs are unwound along the slot. The lateral and longitudinal restraint which is thus obtained imparts greater stability to movable slot closures employing this type of closure element than was heretofore obtained.

An object of the present invention is the provision of a movable slot closure in which any tendency for undesirable displacement or distortion of the closure is effectvely minimized.

Another object is to provide a movable slot closure in which means are included which aiford positive restraint for the closure element ,under very adverse service conditions.

A further object of the invention is the provison of a movable slot closure wherein a plurality of means co- Operating with the closure element are included for imparting both longitudinal and lateral restraintto the closure element thus preventing undesirable displacement,

distortion and fleXure of the closure element in response to pressure differentials or wind buffeting.

Still another object is to provide a movable slot closure wherein the restraining means necessary to prevent undesirable dsplacement, distortion and fiexure of the closure element in response to pressure diiferentials, wind b uiieting, or the like, can be accommodated in various sizes and shapes of slot closures, as well as over nonplanar surfaces.

r A final object is to provide a movable slot closure, With characteristics as described in the preceding objects, in which the restraining means provided aiords facile release of the closure from any type of freezing or icing, and pernits jettisoning the slot closure quickly and easily in an emergency.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawing in which:

Fig. 1 shows a broken-away front elevation View of a preferred embodiment of the invention,

Fig. 2 is a cross-sectional View taken on line 2-2 of Fig. 1 showing additional structural details,

Fig. 3 is an expanded cross-sectional view of a Neg'ator spring showing in particular the characteristic outward arcuate dsplacement in the section adjacent the coled portion thereof when the spring is unwound,

Fig. 4 illustrates a cross-sectional View of the movable slot closure associated with a conveX surface, and

Fig. 5 shows an enlarged isometric View, partially broken away, of a modified embodiment of the movable closure, incorporating slightly altered structural details, in operable relation to a segmental portion of a slotted structure having either a planar or non-planar surface.

Referring now to the drawings, in which like numerals refer to like or corresponding parts throughout the several views, in Fig. l, the instant invention is illustrated as being incorporated in a slot closure device which is effective to seal in that portion of a housing indicated by reference character and provided with a traverse slot 12, through which a projecting element such as a gun barrel, camera lens, shafts, or the like, may protrude for recprocally traversable movement along the length of slot 12. A dolly mechanism provided with a suitable aperture or apertures 16 to receive such a projecting element may be mounted for sliding movement along the slot 12 and be arranged to close the portion of the slot immediately adjacent to an element projecting through the slot. A pair of equally stressed Negator springs 18 may conveniently be rotatably mounted in opposed positions adjacent the projecting element by means of a pair of bracket assemblies 19 secured to the opposite ends of dolly mechanism 14 by suitable fasteners which may be rivets 28, as shown. The spindle 27 on which each spring 18 is coled is secured to its respective bracket assembly 19 by means of a suitable retaining collar 29. With the outer extremities of the extended portions 20 of springs 18 held stationary at the opposite ends of slot 12, as by clamping means 17, the "Negator springs 18, respectively, wind and unwind, with sliding movement of dolly mechanism 14 to form a continuous slot closure, eecting sealable engagement with gaskets 21, as the projecting element encircled by dolly mechanism 14 is traversed.

In that portion of the housing 10, which defines the edges immediately adjacent slot 12, are contained a series of short pins 22 fixedly mounted along the edges of slot 12, and projecting outwardly therefrom so that the pins 22 are disposed perpendicularly to the adjacent portion of housing 10. The pins 22 may be fixedly mounted in the edges of housing 10 along the longitudinal edges of slot 12 by any appropriate means, such as that illustrated in the cross-sectional View of Fig. 2, wherein a pin is shown to be engaged with a threaded Washer 25, and locked securely to housing 10 with nut 24. It should be noted that the scale in the view of Fig. 2 is expanded in order to illustrate in detail the relationship between the pins 22 and the associated members. The spacing and arrangement of the respective series of pins 22 may be varied as necessary to meet varying Operating conditions, and both the longitudinal shape and the crosssectional shape of the respective pins may be modified, of course, from the simple cylirrdrical form and circular cross-section, as shown. For cooperation with the series of projecting pins 22, the opposite edges of springs 18 must be provided with a corresponding series of perforations 23, which are engaged with the pins 22 as either spring 18 is extended along the slot, in the manner best illustrated in Fig. 2.

The assurance of immediate engagement of the perforations 23 with pins 22 in the instant invention is attributable to a singularly significant property of the Neg'ator spring, best seen in Fig. 3. It is fundamental to note that the outer turn of spring 18 exhibits at all times a pronounced outward arcuate dsplacement, which is substantially independent of the number of turns on the coled portion, as illustrated for both limit positions of the coil, thus directly providing for a positive forcible eugagement between the pins and holes without the provisions of special means for achieving this end. Hence, integrity of the seal between the extended spring element 20 and gasket 21 bordering the longitudinal edges of the slot is assured.

The distinctive characteristc properties of Neg'ator springs together with the positive restraining means hereinbefore denoted combinatively provide for unique applicability of the inventive movable slot closure to both planar and non-planar surfaces, but especially, to those surfaces possessing convex curvatures. Thus, in Fig. 4 the instant invention is illustrated associated with a convex surface, although it should be understood that operation is not exclusively restricted to this type of surface curvature. It is deemed that the slot closure may be arranged to cooperate with a surface having a concave curvature.

The operation of the movable slot closure can best be described in connection with the expanded isometric showing in Fig. 5, in which certain possible variations in the detail construction of the various elements are also illustrated. In this view, dolly mechanism 14' contains only a single aperture 16, and the bracket assemblies 19' are unitary elements as compared with the 'built-up assemblies 19 illustrated in Fig. 1, although the attachment of bracket assemblies 19' to the dolly mechanism 14' is accomplished in the manner shown in Fig. 1. Other mnor variations include a change in the configuration of the spacing between perforations or holes 23 from a staggered arrangement to transversely aligned pairs of holes, and a corresponding relocation of the pins 22. Since none of the changes mentioned above amounts to a basic modification, the operation of the movable closure as depicted in either Fig. l or Fig. 5 is the same.

In operation, as dolly mechanism 14' shown in Fig. 5 is traversed along the slot 12, the pair of opposed Neg'ator` springs 18, the outer extremities of which are fixedly secured at the opposite ends of slot 12, as shown in Fig. l, wind and unwind from the coled portions thereof rotatably supported upon the dolly mechanism 14' to cover the portions of the slot 12 which are not occupied by the dollymechansm 14'. Coincident with the traversal of the dolly mechanism, an uncoiling force directly effects a continuous outward arcuate dsplacement of a portion immediately adjacent the coled portion of respective springs 18, as best observe'd in either Fig. 3 or Fig. 5. As either spring 18 is unwound to form an extended spring element 20, which is laid in contact with the gaskets 21 mounted along the longitudinal edges of slot 12, the series of perforations or holes 23' in the outwardly arcuately displaced portions are promptly 'brought into positive engagement with the series of pins 22 fixedly mounted along the edges of slot 12 and projecting through the gaskets l r I 21, as portrayed in either Fig. 1 or Fig. 5. Hence, pins 22, engaging the extended spring elements 20 by means of the holes 23 therethrough, restrain the edges of the spring elements 20 against lateral displacement thereof to` preclude misalignment of the spring elements with the slot and prevent collapse of the springs through the slot under adverse conditions such as a substantial pressure diiferential. In addition, the engagement of the pins 22 in the holes 23 of the spring elements 20 prevents longitudinal displacement of the adjacent portions of the spring elements 20, thereby largely overcoming the tendency for extended spring elements 20 to breathe in response to pressure difierentials or buffeting incurred, for example, during fiight of an aircraft in which a slot closure constructed according to the teachings of the instant invention is installed. Since breathing of the spring elements 20 involves aminute lengthening of the extended spring elements 20 without movement of the dolly mechanism 14', this additional length must be supplied by a small angular deflection of the tightly coiled 'portion of each spring 18 rotatably supported on the dolly mechanism 14' and free to rotate in this manner in previously known slot closures of this type. However, in the configuration of the slot closure taught here, there are always pins 22 engaging holes 23 in the exteuded spring elements 20 im,- mediately adjacent to the coiled portions of the springs 18, regardless of the instantaneous position of the dolly mechanism 14', that efectively preclude any angular displacement of the coiled portions of the springs 18 and thereby prevent breathing of the extended spring elements 20. With flexure of the spring elements thus limited to the relatively short spans between successive pins 22, the adverse efiect of this limited flexure can be overcome by using sufiiciently thick and resilient gaskets 21 beneath the edges of the extended spring elements 20. The significant advantage of this invention is contingent upon the fact that springs 18, as Negator" elements, inherently 'wind tightly on themselves forming compact solid coils,

thus precluding relative windng movement of one end of the spring when the other is fixed, as described above.

Notwithstanding the adaptabilty of Negator springs for use as slot closure devices, their potentiality as a movable slot closure affording a positive seal is not fully realized unless the blank from which the Neg ator is formed is initially laterally prestressed previous to being shaped into a spring element, as shown in final form by the portion of Fig. 1 designated by reference character 18. This prestressing operation is efiective to oifset the inherent tendency' of' spring element 20 to curl laterally along-the unwound extended portions, toward the side of the extended portion on which the coiled portion is disposed. This, tendency is not only detrimental to full cooperation between the projecting pins 22 and corresponding respective holes 23, but also may cause spring element 20 to collapse through the relatively narrower slot 12, if this curl is not eliminated. This lateral prestressing of spring blanks can most effectively be accomplished by the following procedure: Before the strip of spring material comprising the blank is treated to form a Neg`ator spring and while it remains flat throughout its entire length, the material is laterally curved about an axis parallel to its length in a brake suitable for this purpose. The curvature assumed by the material in prestressing is the result of cumulative incremental deflections in a direction opposite to the direction in which it will be deflected as it is longitudinally coiled and an amount sufficient to oppose the springs natural tendency to curl in the opposite direction when it is formed into a Negator unit by a suitable coiling operation. This prestressing, as a result, enables the modified "Neg`ator spring used as a closure element to make the most effective use of pins 22 in cooperation with openings 23, as shown in the accompanying drawings, since the edges of extended spring elements 20 press more efiectively on gaskets 21 than heretofore as with Neg'ator" springs which are not initially prestressed.

While the degree of sealing provided by the illustrated embodiments shown in Fig. l and Fig. 5 is satisfacto'y in many applications, specific circumstances, such as requirements for heating or pressurizing a turret assembly, may'require a complete sealing arrangement for the slot 12 including an adjustable scaling means between theends of the dolly mechanism and the coiled portions of the respective springs such as a resilient or otherwise adjustable element mounted to continuously fill this space which varies in width as the springs are wound and unwound. Alternatively, a modified form of bracket assemblies 19 or 19' could be rendered continuously adjustable for scaling purposes by pivotal attachments therefor with suitable biasing means effective to maintain the coiled springs in engagement with the dolly as the position of dolly mechanism is changed relative to the slot. In this manner, the enlarged opening that would ordinarily be presented between theends of the dolly mechanismand the coiled spring when the dolly mechanism is at either extremity of its slot travel would 'be eliminated, and the integrity of the closure would be considerably improved in accordance with requirements of the specific circumstances.

The instant invention as described, affords positive restranng action in movable slot closures employing "Neg ator springs as closure elements. The restrain'ng means as herein provided prevent displacement and distortion of the closure element in response to pressure diferentials, wind bufietng or the like, that may be encountered, for example, in a turret installation of an aircraft in flight. The structure of the instant invention is very little restricted in application, accommodating various sizes and shapes of slot openings as well as surfaces of V claims.

What is claimed is:

1. In a movable closure for an elongated opening in a structure having a dolly means adapted to receive a protruding element and mounted for movement along the elongated opening, and a pair of negative springs requiring application of a force for uncoiling them respectively including coiled portions rotatably mounted on said dolly means and eXtended uncoiled portions terminating in outer ends which are fixedly held 'With securing means v to the opposite ends of said elongated opening, said extended uncoiled portions of said negative springs together with said dolly means forming a closure for said elongated opening, said for-ce efiecting a continuous arcuate disp'lacement of a portion immediately' adjacent the respective coiled portions of said negative springs as the dolly means is traversed, the combination with said negative springs of a multiplicity of spaced male retaining means mounted adjacent the respective longitudinal edges of the elongated opening projecting into engagement with a corresponding multiplicity of correspondingly spaced closely interfitted female engaging means in the respective longitudinal edges of said negative springs for immobilizing against incremental longitudinal displacement the entire extended uncoiled portions of said springs relative to the elongated opening, thereby imparting stability and effective sealing to the closure for said elongated opening.

2. In a movable closure for an elongated opening in a structure having a dolly means adapted to receive a pro trudng element and mounted for reciprocal movement along the length of the elongated opening, a pair of'ne-gative springs requiringapplication of a force for uncoiling them and mounted for rotation on opposite ends of said dolly means, said negative springs respectvely including coiled portions and extended uncoled portions terminating at outer ends which are fixedly held by securing means to the respective opposite ends of said elongated opening, said extended uncoiled portions' of said negative springs together With said dolly means forming a olosure for said elongated opening, said force directly ettecting a continuous arcuate displacement of a portion immediately adjacent the respective coiled portions of said negativesprings as the dolly neans is traversed, and resilient gaskets bordering opposite edges and disposed along the length of the elongated opening so as to provide a seal Ifor the closure, the combination with said negative springs of a restraining means comprising a plurality of relatively short cylindrical pins 'with constant diameters throughout their length projecting outwardly from and disposed perpendicaular to the surface of the structure 'bordering the longitudinal edges of said elongated opening, and matching perforations of substantially the same diameter as the pins spaced along the longitudinal edges of said springs that are rolled into juxtaposition for closely interfitted engagement with said perpendicularly disposed pins as said dolly means is traversed along the elongated opening.

3. In a movable closure for an elongated opening in a structure, a dolly means adapted to receive a protruding element and mounted for reciprocal movement along said elongated opening, a matched pair of self-winding coil springs each requiring for uncoiling thereof a substantially constant force that is independent of the amount of deflection thereof and mounted for rotation on opposite ends of said dolly means, said self-Winding coil springs respectvely including tightly coiled portions and extended uncoiled portions terminating in outer ends which are fixed'ly held by securing means to the respective-opposite ends of said elongated opening, said extended un'coiled portions of said self-Winding coil springs forming a closure for the portions of the elongated opening not occupied by the dolly means, said force directly efiecting a continuous arcuate displacement of a portion immediately adjacent the respective coiled portions of said self-winding coil springs as thedolly means is traversed, resilient gasket means bordering opposite edges and disposed along the length of the elongated opening so as to provide a seal with the extended uncoiled portions of said springs covering the elon-gated opening, and restraining means comprising a plurality of relatively short cylindrical pins of a constant diameter throughout their length projecting outwardly from and disposed perpendicular to the surface of the structure bordering the longitudinal edges of said elongated opening and matching perforations of substantially the same diameter as the pins spaced along the longitudinal edges of said springs that are rolled into juxtaposition for closely interfitted engagement with said perpendicularly disposed pins as said dolly means is traversed along the elongated openng.

4. In a movab'le closure for a slot in a turret, a dolly means having an aperture to receive therein a gun barrel and slida'ble along the length of said slot, supporting means mounted in opposed positions at opposite ends of said dolly means, a first self-Winding coil spring mounted for rotation on one of said supporting means, a second sel'f-winding coil spring mounted for rotation on the other said supporting means, said first and said second self- Winding coil springs requiring a substantially constant and equal force for nncoiling thereof and respectvely including tightly coiled portions and extended uncoiled lengths whose outer ends are fixedly held with clamping means to the respective opposite ends of said slot, said force directly efiectng a continuous arcuate displacement of a portion immediately adjacent the respective coiled portions of said helf-Winding coil springs as the dolly means is traversed, said uncoiled lengths together With said dolly means forming a movable closure for the slot as the dolly means is traversed, resilient gasket means bordering the longitudinal edges and so :disposed along the slot so as to provide a seal With the overlapping surface of the extended uncoiled lengths of said springs covering the slot, a plurality of relatively short cylindrical pins of constant diameter throughout their length projecting outwardly from and disposed perpendicular to the surface of the turret and bordering the longitudinal edges of the slot, and matching perforations of substantially the same diameter as the pins spaced along the longitudinal edges of said springs that are rolled into juxtaposition for closely interfitted engagement With said perpendicularly disposed pins as said dolly means is traversed, said first and said second self-Winding coil springs being initially prestressed to ofiset an inherent tendency for `lateral curling of the extended uncoiled lengths thereof covering the slot, thereby providing a greater intimacy of surface contact between the gasket means and said extended uncoiled lengths for more effective scaling, and providing effective restraint to the extended uncoiled length of said springs against undesirable fiexure and displacement thereof as the dolly means supporting the gun barrel is traversed along the length of the slot.

5. The movable closure of claim 4 in which the surface of the turret defining the slot is convex.

References Cited in the file of this patent UNITED STATES PATENTS 549,495 Crocker Nov. 12, 1895 2,034,990 Ewing Dec. 12, 1942 2,601,361 Blatz June 24, 1952 2,811,201 Reid Oct. 29, 1957 OTHER REFERENCES The Negative Spring-A Basic New Elastic Member, by Cook and Clarke, Prod. Eng.-July 1949, pages 136- 140, 

